This post to alt.msdos.batch.nt by Simon Sheppard, based on a previous post by Michael Jerkovic, shows an ingenious way to get today's date in an almost language independent format.
Why "almost"? Because this batch file will fail when the year is not the last part of the date string, as in YYYY-MM-DD (very well possible), or when no delimiters are used, as in DDMMYYYY (highly improbable).
Contrary to my own SortDate (3.*) solution which uses REGEDIT, Simon's/Michael's solution only uses internal commands.